Objective: To evaluate the expression of cyclooxygenase-2 (COX-2) and Ki-67 in primary and recurrent pterygia. Material and Methods: Pterygium excision together with limbal/conjunctival autografting was performed in primary and recurrent pterygium cases who did not have clinically evident inflammatory findings. The excised tissues were stored at -80 degrees C for the analysis. Ki-67 expression was determined with only immunohistochemically while COX-2 expression was determined with both immunohistochemistry and real-time polymerase chain reaction, which is a more sensitive method. Normal human conjunctival samples from age-matched donors were used as controls. Results: Twelve primary and nine recurrent pterygium tissues were included in the study group. The expression of COX-2/beta actin mRNA was not significantly different in primary pterygia, recurrent pterygia and normal conjunctival tissues (0.0082 +/- 0.0038, 0.0094 +/- 0.0023, and 0.0075 +/- 0.0035 respectively (p=0.32). The expression of Ki-67 nuclear antigen was significantly higher both in primary and recurrent cases when compared to control group (5.2 +/- 5.0%, 7.1 +/- 2.% and 1.29 +/- 0.9% respectively (p=0.018 and p= 0.001, respectively). There was no significant correlation between immunohistochemical expression of Ki-67 and COX-2 in primary and recurrent pterygium tissues (p=0.281, r=0.339; p=0.649, r=-0.177, respectively. Conclusion: COX-2 expression does not seem to increase in clinically uninflamed primary and recurrent pterygia tissues. Increased Ki-67 expression in primary and recurrent pterygia supports the proliferative nature of the disease which might have implications in regard to treatment options.